1. Field of the Invention
The invention relates to apparatus and methods that provide protection from electrostatic discharge (ESD). More particularly, the invention relates to apparatus and methods that provide protection from electrostatic discharge in display systems, such as avionics display systems.
2. Description of the Related Art
In electronic systems, many devices have been developed to provide protection from electrostatic discharge (ESD). Electrostatic discharge, which is the transfer of charge between bodies at different electrical potentials, can alter the electrical characteristics of electronic devices and components, or even degrade or destroy their normal operation, causing equipment malfunction and failure. Therefore, it is important to control the discharge static electricity buildup from such electronic devices and their components.
One manner to provide ESD protection in various electronic devices is to create an electrically conductive path between the device and its conductive frame or support member to allow for electrostatic discharge from the device to the frame. For example, in electronic display systems, such as those used in avionics and in military applications, an electrically conductive gasket (an ESD gasket) or other interface apparatus is secured between an electrically conductive display panel and its electrically conductive support structure to provide ESD protection for the display panel. In such display systems, ESD protection is crucial to maintaining proper operation of the displays.
Conventionally, ESD gaskets are configured as wires or other conductors embedded in a foam or rubber compound, which typically is then clamped between the conductive display panel and its conductive frame. Another type of conventional ESD gasket is made of fabric strips or other non-conductive substrates that are wrapped or coated with conductive material, such as conductive strips. Yet another conventional ESD gasket is a spring finger gasket, made of beryllium and/or copper, that often is attached between the display panel and its frame.
However, conventional ESD gaskets do not provide a sufficiently low resistance and/or a sufficiently secure conductive bond between the conductive structures. For example, many conventional ESD gaskets have difficulty in establishing and maintaining relatively low impedances at the mating surfaces of the conductive structures because of the relatively large pressures that are needed to maintain solid electrical contact, especially when both mating surfaces are planar surfaces. Conventional springs, clips, clamps, screws and other mechanical fastening means for maintaining contact between the ESD gaskets and their conductive mating surfaces often do not keep the EDS gaskets secured between the mating surfaces. Also, such mechanical fastening devices constitute additional component parts that must be maintained in inventory, and the use of such parts tends to increase assembly time and overall cost. However, less burdensome means, such as conductive adhesives, do not allow direct contact between the ESD gaskets and their conductive mating surfaces. Thus, since the electrical resistance of such conductive adhesives is much greater than the resistance of the ESD gasket, the electrical conductance of the path between the mating surfaces through the ESD gasket is greatly reduced, thereby reducing the effectiveness of the ESD gasket to control ESD.
Therefore, it would be desirable to have an interface apparatus like an ESD gasket to provide and securely maintain a relatively low resistance path between two conductive surfaces, such as in a conductive panel and its support structure in a display system.